Inert fluids, such as argon, krypton, xenon and helium are being used more and more in the electronics industry.
For this reason, there is an increasing demand for ultrapure inert fluids, in particular argon and helium, that is to say ones which are substantially free of the impurities which they contain, such as impurities of the following types: oxygen (O.sub.2), carbon monoxide (CO), nitrogen (N.sub.2), carbon dioxide (CO.sub.2), hydrogen (H.sub.2) and hydrocarbons (methane, etc.).
There are many documents dealing with the purification of inert fluids, in particular the purification of liquid argon or argon gas with respect to its impurities nitrogen and oxygen, which impurities may be found in argon at concentrations which can vary depending on the way in which they are produced, to be precise, up to 1000 ppb for oxygen and from 500 to 2000 ppb for nitrogen.
The following documents may, in particular, be cited: JP-A-5818777, JP-A-59223203, JP-A-7138007, JP-A-3164410, JP-A-5461091, AU-A-659759, U.S. Pat. No. 5,204,075, EP-A-606848, U.S. Pat. No. 5,419,891, U.S. Pat. No. 5,159,816, EP-A-514163, U.S. Pat. No. 4,983,199 and U.S. Pat. No. 3,928,004.
According to these documents, the impurities N.sub.2 and O.sub.2 contained in argon are generally removed by adsorption on a zeolite of the following types: X, A, mordenite or chabazite, optionally exchanged by cations such as the cations Li, K, Ca, Sr, Ba, Mg, etc.
However, these various processes for purifying inert fluids, in particular argon, cannot be regarded as fully satisfactory given that, in general, they are not suitable for obtaining ultrapure fluids that can be used directly in the field of electronics.
This is because the specifications governing the electronics industry require inert fluids substantially free of all their major impurities, such as the impurities N.sub.2, O.sub.2 and hydrocarbons, in the case of argon, that is to say containing a maximum level of the order of 1 ppb for each of the impurities.
At present, most known processes only make it possible to obtain partially purified inert fluids, in particular argon, that is to say containing more than 100 ppb of impurities, in particular N.sub.2 and O.sub.2, and usually more than 1 ppm of O.sub.2 and N.sub.2 impurities.
However, such levels of impurities are unacceptable in the field of electronics because these impurities can react with the materials and electronic components, such as printed circuits, and cause damage to them.
Furthermore, the problem of purifying inert fluids with respect to their hydrocarbon impurities, in particular methane (CH.sub.4), has not, or has not completely, been solved to date.
However, impurities of the hydrocarbon type are found in inert fluids, in particular in argon, especially argon produced using a process combining cryogenic distillation and hot catalytic de-oxygenation in the presence of industrial hydrogen, which hydrogen often contains traces of impurities of the CH.sub.4 type, at levels which may be up to 400 ppb, as has been shown by analyses carried out at the production site, that is to say, at levels which may be comparable with the level of oxygen impurities, which oxygen is considered with nitrogen to be a major pollutant of argon.